Is fecal-oral transmission possible?
In several studies in pediatric and adult populations, the fecal elimination of SARS-CoV-2 was found to be prolonged for several weeks, which has led to speculating a possible fecal-oral transmission.14,15 The fecal-oral transmission route has also been previously demonstrated for other coronaviruses, such as MERS-CoV. However, it has been argued that the positivity of reverse transcriptase-polymerase chain reaction (RT-PCR) for SARS-CoV-2 on rectal swab or stool does not imply that it is vital and able to infect other subjects. A study by Wang et al. including 205 patients with SARS-CoV-2 infection (more than one thousand samples from blood, sputum, feces, urine, nasal swab, and other biological samples) is particularly noteworthy.16 Fecal samples were positive in 29% of cases; moreover, four samples revealed a vital virus after culture, possibly transmitting the infection.
In adults, RT-PCR positivity on stool samples in patients diagnosed with COVID-19 varies between 6 and 53.4% across studies. It is interesting that in some case-series, around 20% of the fecal samples resulted positive even after that RT-PCR on pharyngeal swab had turned negative.15 Therefore, a fecal-oral transmission might also be possible in asymptomatic or convalescent patients.
Similar findings have been observed in children. In a Chinese study, 8 out of 10 children were still positive for RT-PCR on the rectal swab for a few days after RT-PCR negativization on nasopharyngeal swabs.16 Some authors suggested that serial rectal swabs should be performed over time before declaring the child non-infectious. In a recent case series, including 22 children with documented SARS-CoV-2 infection, fecal RNA shedding was observed in 68% of patients independently from gastrointestinal symptoms. The estimated positivity on day 14 from symptom onset was 52% for a nasopharyngeal swab and 31% for stool swab.17 In another Italian study, two pediatric cases with RT-PCR positivity on stool were reported. The pediatric literature available at publication date was reviewed, including overall 13 children affected by SARS-CoV2 infection with a positive RT-PCT on the stool and/or rectal swab.9 Authors suggest that negativity in both nasopharyngeal and stool samples might be a standard requirement for the cessation of mandatory isolation.